Recently, with the rapid development of semiconductor and communication technologies, mobile communication terminals have been widely popularized to the extent that they are used as portable devices nationwide. Furthermore, with the advent of new technology, new models having various types of functions are successively marketed, and rapidly replace out-of-date models.
Meanwhile, in the case of mobile communication terminal manufacturers, it is necessary for each mobile communication terminal manufacturer to ascertain the quality of actual communication speech of each terminal, which it has manufactured, in order to manufacture terminals of the highest quality. Furthermore, even in the case of mobile phone companies, it is necessary for each mobile phone company to ascertain the quality of actual communication speech of each terminal in order to check and optimize the performance and conditions of mobile communication networks that it operates and maintains. As a method of evaluating the quality of actual communication speech, the MOS has been proposed. The MOS is a subjective measurement method that evaluates the quality of communication speech based on five levels, which are indicated in the following table 1, by causing a plurality of users to listen to the communication speech, representing the degree of user satisfaction as scores, and obtaining the average of the scores.
TABLE 1MOS ValueQuality Level5Excellent4Good3Fair2Poor1Bad
The MOS measurement method is a subjective measurement method, as described above, and thus the objectivity thereof is low and, at the same time, the cost of taking measurements is high, therefore automated and objective methods have recently been preferred. In greater detail, there are Perceptual Speech Quality Measurement (PSQM), defined in ITU-T P.861, and Perceptual Evaluation of Speech Quality (PESQ), defined in ITU-T P.862 to respond to packet loss and the like based on the PSQM.
Meanwhile, the above-described MOS measurement method can be performed in such a way as to measure the quality of actual communication speech between mobile communication terminals or the quality of actual communication speech between a mobile communication terminal and a wired telephone. In this case, an MOS value may change according to actual communication speech between the two communication terminals, and thus the reliability of MOS values is assured only when the actual communication speech is appropriately controlled.
However, conventional measurement equipment, in which the above-described MOS measurement algorithm is installed, is configured such that a tester manually and directly controls the volume level of communication speech, so that it is problematic in that the probability of the occurrence of a manipulation error still exists, in particular, in that, even though the tester controls the communication speech to a predetermined value, an MOS value can change because the volume level of actual communication speech varies according to the mobile communication network environment or the characteristics of each mobile communication terminal.
Furthermore, conventionally, when a tester is spaced apart from counterpart measurement equipment, he or she must move to the counterpart measurement equipment in order to control the volume level of the counterpart measurement equipment, therefore there are problems in that the usage thereof is inconvenient and a lot of measurement time and a considerable amount of man power are required.